JP6102661B2 - Engine exhaust gas recirculation control device - Google Patents

Description

  The present invention belongs to a technical field related to an exhaust gas recirculation control device for an engine.

  Conventionally, it is known to provide a high pressure EGR passage and a low pressure EGR passage in order to recirculate a part of the exhaust gas of the engine from the exhaust passage to the intake passage (see, for example, Patent Document 1). The high-pressure EGR passage includes an exhaust passage on the upstream side of the turbine of the exhaust turbocharger and a downstream side of the compressor of the exhaust turbocharger (more specifically, a downstream side of an intercooler disposed on the downstream side of the compressor). ) To the intake passage. The low pressure EGR passage connects the exhaust passage on the downstream side of the turbine and the intake passage on the upstream side of the compressor. The low pressure EGR passage is provided with a low pressure EGR valve that changes the cross sectional area of the low pressure EGR passage, and the high pressure EGR passage is provided with a high pressure EGR valve that changes the cross sectional area of the high pressure EGR passage. Yes.

  In the above-mentioned Patent Document 1, during the idling operation of the engine, by increasing the flow rate of the low-pressure EGR gas in the low-pressure EGR passage, the deposit caused by the condensed water is removed, and the deformation of the compressor by the deposit and the intercooler I try to prevent clogging.

JP 2007-291973 A

  By the way, at the time of idling of the engine, the start response (acceleration) of the vehicle is improved by keeping the turbine of the exhaust turbocharger rotated. For this purpose, it is preferable to increase the recirculation amount of the exhaust gas through the low pressure EGR passage as much as possible.

  However, if the recirculation amount of the exhaust gas through the low pressure EGR passage is increased, condensed water is likely to be generated as described in Patent Document 1, and if the idling operation is continued for a long time, the condensed water is accumulated in the intercooler, and the engine is operated as it is. When stopped, the condensed water may freeze in the intercooler.

  The present invention has been made in view of such points, and an object of the present invention is to improve the vehicle start response in exhaust gas recirculation control during idle operation of the engine and to condense water in the intercooler. This is to prevent the accumulation of water.

  In order to achieve the above object, according to the present invention, an exhaust turbocharger having a turbine disposed in an exhaust passage of an engine and a compressor disposed in an intake passage, and the intake air downstream of the compressor. An intercooler disposed in the passage, a low pressure EGR passage connecting the exhaust passage on the downstream side of the turbine and the intake passage on the upstream side of the compressor, and the low pressure EGR passage. A low pressure EGR valve that changes the cross-sectional area of the passage, a high pressure EGR passage that connects the exhaust passage upstream of the turbine and the intake passage downstream of the intercooler, and the high pressure EGR passage; High-pressure EGR valve that changes the cross-sectional area of the high-pressure EGR passage, and valve control that controls the opening of the low-pressure EGR valve and the high-pressure EGR valve And a shift range detecting means for detecting a shift range of a transmission of a vehicle on which the engine is mounted. The valve control device includes: During idle operation, when the shift range detected by the shift range detecting means is a non-traveling range, the total exhaust gas of the engine through the low-pressure EGR passage and the high-pressure EGR passage is greater than when the shift range is a traveling range. The opening of the low-pressure EGR valve and the high-pressure EGR valve is controlled so that the ratio of the recirculation amount of the exhaust gas through the high-pressure EGR passage to the recirculation amount is increased.

  With the above configuration, when the engine is in idling operation, when the transmission shift range is the non-traveling range (P range, N range), it is lower than the traveling range (D range, R range, etc.). Since the ratio of the exhaust gas recirculation amount through the high pressure EGR passage to the total exhaust gas recirculation amount through the EGR passage and the high pressure EGR passage is increased, the exhaust gas recirculation amount through the low pressure EGR passage is reduced or becomes zero. Thus, it is possible to prevent the condensed water from accumulating in the intercooler. Even if the exhaust gas recirculation amount through the low-pressure EGR passage is reduced in this way, when the transmission shift range is the non-traveling range, the vehicle driver's willingness to travel is low and the vehicle start-up response problem does not occur. . On the other hand, when the shift range of the transmission is the travel range, the start ratio of the vehicle can be improved by reducing the ratio, and the intake passage (especially from the compressor to the intercooler) can be improved during idle operation. By filling the interior with the exhaust gas recirculated through the low pressure EGR passage, the exhaust gas recirculation through the high pressure EGR passage can be reduced without reducing the total recirculation amount of the exhaust gas through the low pressure EGR passage and the high pressure EGR passage immediately after the start of the vehicle. Since the turbine flow rate can be secured by reducing the ratio of the recirculation amount, the exhaust gas purification performance can also be improved. Thus, when the shift range is the traveling range, even if the exhaust gas recirculation amount through the low pressure EGR passage is increased, the possibility that the vehicle will start in a short time is high. When the vehicle starts, the condensed water collected in the intercooler is sucked into the engine.

  The engine exhaust gas recirculation control device further includes an intake air temperature detection means for detecting the temperature of the intake air taken into the intake passage, and the valve control device is configured to detect the intake air temperature when the engine is idling. When the temperature of the intake air detected by the above is lower than a predetermined temperature, the opening of the low pressure EGR valve is set to 0% regardless of the speed range detected by the speed range detecting means. Is preferred.

  Accordingly, when the temperature of the intake air (intake air temperature) is lower than a predetermined temperature (for example, 0 ° C. to 5 ° C.), that is, when the condensed water is likely to accumulate in the intercooler and the condensed water is likely to freeze, the low pressure EGR passage By preventing the exhaust gas from recirculating due to the above, it is possible to reliably prevent the condensed water from accumulating in the intercooler and freezing.

  In the exhaust gas recirculation control apparatus for an engine, the high pressure EGR passage includes a cooler side passage in which a high pressure EGR cooler for cooling exhaust gas passing through the engine is disposed, and a cooler bypass side that bypasses the high pressure EGR cooler. The high-pressure EGR valve is disposed in the cooler-side passage, and is disposed in the cooler-side passage, the cooler-side EGR valve that changes the cross-sectional area of the cooler-side passage, and the cooler bypass-side passage. A cooler bypass side EGR valve that changes the cross-sectional area of the cooler bypass side passage, and further includes cooling water temperature detecting means for detecting the temperature of the engine cooling water, and the valve control device is provided during idle operation of the engine. When the temperature of the cooling water detected by the cooling water temperature detecting means is lower than a preset temperature, the upper temperature is increased by the high pressure EGR passage. When performing the reflux exhaust gas, the opening of the cooler-side EGR valve is configured to 0%, it is preferable.

  That is, when the temperature of the cooling water (cooling water temperature) is lower than the set temperature (for example, 50 ° C. to 60 ° C.) (that is, when it is cold before the completion of warming), it is condensed at the location of the high pressure EGR cooler in the cooler side passage. Water is generated, which mixes with the straw and deposits. In particular, since the exhaust gas flowing through the high pressure EGR passage is the one before passing through the exhaust purification device, it contains a large amount of soot. Therefore, deposits are likely to occur, and the deposits clog the cooler side passage. . Therefore, when the coolant temperature is lower than the set temperature, the opening of the cooler side EGR valve is set to 0%, so that the cooler side passage can be prevented from being clogged with deposits.

  In the exhaust gas recirculation control device for the engine, the valve control device is in a state where the travel range is in the travel range even when the shift range detected by the shift range detection means is the travel range during the idling operation of the engine. The opening of the low-pressure EGR valve and the high-pressure EGR valve is controlled so that the ratio is the same as that in the non-traveling range when continuing for a predetermined time or more. Is preferred.

  As a result, when the state where the shift range is the travel range continues for a predetermined time or longer, a large amount of condensed water accumulates in the intercooler by setting the ratio to the same high ratio as when the shift range is the non-travel range. Can be prevented.

  In the exhaust gas recirculation control device for the engine, when the engine is in idle operation, the transmission transmission force of the transmission is reduced when the shift range of the transmission is the travel range and the brake pedal is depressed. The valve control device further includes a drive transmission force reduction means that causes the drive transmission force reduction means to operate even when the shift range detected by the shift range detection means is a travel range during idle operation of the engine. When the drive transmission force is reduced, the openings of the low pressure EGR valve and the high pressure EGR valve are controlled so that the ratio becomes the same ratio as that in the non-traveling range. Is preferable.

  That is, even if the shift range is the travel range, when the drive transmission force of the transmission is reduced by the drive transmission force reducing means, the brake pedal is depressed, so the vehicle driver's intention to travel is low. Even at this time, it is possible to prevent the condensed water from accumulating in the intercooler as much as possible by setting the ratio to the same high ratio as in the non-traveling range.

  As described above, according to the exhaust gas recirculation control device for an engine of the present invention, the low pressure EGR is lower when the transmission is in the non-traveling range when the engine is idling than when it is in the traveling range. When the ratio of the recirculation amount of the exhaust gas through the high-pressure EGR passage to the total recirculation amount of the engine exhaust gas through the passage and the high-pressure EGR passage is increased, The start response of the vehicle and the exhaust gas purification performance can be improved, and when the intention to start is low, it is possible to prevent the condensed water from accumulating in the intercooler.

It is a figure showing a schematic structure of an engine controlled by an exhaust gas recirculation control device concerning an embodiment of the present invention. It is a block diagram which shows the structure of the control system of an exhaust gas recirculation | reflux control apparatus. It is a figure which shows the map for determining low pressure EGR target recirculation amount and high pressure EGR target recirculation amount based on engine speed Ne and engine load PE. 3 is a flowchart showing an exhaust gas recirculation control operation by a control unit. It is a flowchart which shows another exhaust-gas recirculation | reflux control operation | movement by a control unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of an engine 1 controlled by an exhaust gas recirculation control apparatus according to an embodiment of the present invention. The engine 1 is a diesel engine mounted on a vehicle, and includes a cylinder block 3 provided with a plurality of cylinders 2 (only one is shown in FIG. 1), and a cylinder disposed on the cylinder block 3. And a head 4. In each cylinder 2 of the engine 1, pistons 5 are fitted so as to be able to reciprocate. A deep dish-shaped combustion chamber 6 is formed on the top surface of the piston 5. The piston 5 is connected to the crankshaft 8 via a connecting rod 7. The engine 1 is provided with an engine speed sensor 9 that detects the rotational speed of the engine 1 by detecting the rotational angle position of the crankshaft 8.

  In the cylinder head 4, an intake port 12 and an exhaust port 13 are formed for each cylinder 2, and an intake valve 14 and an exhaust valve that open and close the opening of the intake port 12 and the exhaust port 13 on the combustion chamber 6 side. 15 are arranged respectively.

  The cylinder head 4 is provided with an injector 17 for injecting fuel. The injector 17 is arranged so that its fuel injection port faces the combustion chamber 6 from the ceiling surface of the combustion chamber 6 so that fuel is directly injected and supplied to the combustion chamber 6 near the top dead center of the compression stroke. It has become.

  The engine 1 is equipped with a variable valve lift mechanism (hereinafter referred to as VVL) 16 that adjusts the lift amounts of the intake valve 14 and the exhaust valve 15. The VVL 16 can adjust the lift amount so that the intake valve 14 and the exhaust valve 15 are fully closed or substantially fully closed.

  An intake passage 30 is connected to one surface of the engine 1 so as to communicate with the intake port 12 of each cylinder 2. An air cleaner 31 that filters intake air is disposed at the upstream end of the intake passage 30, and the intake air filtered by the air cleaner 31 passes through the intake passage 30 and the intake port 12 and is a combustion chamber of each cylinder 2. 6 is supplied.

  Near the downstream side of the air cleaner 31 in the intake passage 30, there are an air flow sensor 32 that detects the flow rate of the intake air sucked into the intake passage 30, and an intake temperature sensor 33 that detects the temperature (intake air temperature) of the intake air. Intake air temperature detecting means). A surge tank 34 is disposed near the downstream end of the intake passage 30. The intake passage 30 on the downstream side of the surge tank 34 is an independent passage branched for each cylinder 2, and the downstream end of each independent passage is connected to the intake port 12 of each cylinder 2.

  Further, a compressor 20 a of the exhaust turbocharger 20 is disposed between the air flow sensor 32 or the intake air temperature sensor 33 and the surge tank 34 in the intake passage 30. The intake air is supercharged by the operation of the compressor 20a.

  Furthermore, between the compressor 20a and the surge tank 34 of the exhaust turbocharger 20 in the intake passage 30, an intercooler 35 that cools the air compressed by the compressor 20a in order from the upstream side, and an intake shutter A valve 37 is provided. The intake shutter valve 37 adjusts the amount of intake air into the combustion chamber 6 of each cylinder 2 by changing the cross-sectional area of the intake passage 30 at the portion where the intake shutter valve 37 is disposed.

  An exhaust passage 40 for discharging exhaust gas from the combustion chamber 6 of each cylinder 2 is connected to the other surface of the engine 1. The upstream portion of the exhaust passage 40 is constituted by an exhaust manifold having an independent passage branched for each cylinder 2 and connected to the outer end of the exhaust port 13 and a collecting portion where the independent passages gather. Yes. A turbine 20b of the exhaust turbocharger 20 is disposed in the exhaust passage 40 on the downstream side of the exhaust manifold. The turbine 20b is rotated by the exhaust gas flow, and the compressor 20a connected to the turbine 20b is operated by the rotation of the turbine 20b.

  A VGT throttle valve 21 is provided in the exhaust passage 40 in the vicinity of the upstream side of the turbine 20b, and the flow rate of the exhaust gas to the turbine 20b is controlled by controlling the opening degree (throttle amount) of the VGT throttle valve 21. Therefore, the rotational speed of the turbine 20b rotated by the exhaust gas flow, that is, the pressure ratio of the compressor 20a of the exhaust turbocharger 20 (from the compressor 20a to the gas pressure immediately before flowing into the compressor 20a) can be adjusted. The ratio of the gas pressure immediately after the outflow of the gas can be adjusted.

  An exhaust gas purification device 43 that purifies harmful components in the exhaust gas is disposed downstream of the turbine 20b of the exhaust turbo supercharger 20 in the exhaust passage 40. The exhaust gas purification device 43 is disposed on the upstream side of the particulate filter 44 that collects particulates such as soot in the exhaust gas, and upstream of the particulate filter 44, and carries platinum or platinum-added palladium. It is disposed downstream of the oxidation catalyst 45 that oxidizes CO and HC in the exhaust gas and the particulate filter 44, and processes (traps) NOx in the exhaust gas, so that NOx is discharged to the atmosphere. And a lean NOx catalyst 46 to be suppressed. The particulate filter 44 and the oxidation catalyst 45 are accommodated in a first case 81, and the lean NOx catalyst 46 is accommodated in a second case 82 different from the first case 81. The second case 82 is disposed away from the first case 81 on the downstream side.

  The engine 1 is configured such that a part of the exhaust gas is recirculated from the exhaust passage 40 to the intake passage 30. In order to recirculate the exhaust gas, a high pressure EGR passage 50 and a low pressure EGR passage 60 are provided.

  The high pressure EGR passage 50 connects the exhaust passage 40 on the upstream side of the turbine 20 b of the exhaust turbocharger 20 and the intake passage 30 on the downstream side of the intercooler 35. More specifically, the high-pressure EGR passage 50 includes a portion between the exhaust manifold 40 in the exhaust passage 40 and the turbine 20 b of the exhaust turbocharger 20, and between the intake shutter valve 37 and the surge tank 34 in the intake passage 30. Connect the part.

  The high-pressure EGR passage 50 has a cooler side passage 51 for cooling and recirculating the exhaust gas, and a cooler bypass side passage 52 for recirculating the exhaust gas at the same temperature. The cooler side passage 51 is provided with a high pressure EGR cooler 53 for cooling the exhaust gas passing through the inside. The cooler bypass side passage 52 is a passage that bypasses the high-pressure EGR cooler 53. A cooler-side EGR valve 54 that changes the cross-sectional area of the cooler-side passage 51 is disposed downstream of the high-pressure EGR cooler 53 in the cooler-side passage 51, and the cooler bypass-side passage 52 includes a cooler bypass-side passage 52. A cooler bypass EGR valve 55 for changing the cross-sectional area is provided. The cooler side EGR valve 54 and the cooler bypass side EGR valve 55 constitute a high pressure EGR valve, and the amount of exhaust gas recirculation through the high pressure EGR passage 50 (the cooler side passage 51 and the cooler bypass side passage 52) is adjusted.

  The low pressure EGR passage 60 connects the exhaust passage 40 on the downstream side of the turbine 20b and the intake passage 30 on the upstream side of the compressor 20a. More specifically, the low pressure EGR passage 60 includes a portion of the exhaust passage 40 between the particulate filter 44 and the lean NOx catalyst 46 (a portion between the first case 81 and the second case 82), and the intake passage 30. Is connected to the portion between the air flow sensor 32 or the intake air temperature sensor 33 and the compressor 20a. The low pressure EGR passage 60 is provided with a low pressure EGR cooler 61 for cooling the exhaust gas passing through the inside. A low-pressure EGR valve 62 that changes the cross-sectional area of the low-pressure EGR passage 60 is disposed downstream of the low-pressure EGR cooler 61 in the low-pressure EGR passage 60.

  An exhaust shutter valve 48 is disposed downstream of the connection portion of the low pressure EGR passage 60 in the exhaust passage 40 (and upstream of the lean NOx catalyst 46). The exhaust shutter valve 48 changes the cross-sectional area of the exhaust passage 40 at the portion where the exhaust shutter valve 48 is disposed. When the cross-sectional area becomes small (the opening degree of the exhaust shutter valve 48 becomes small). In addition, the pressure at the connection portion of the low pressure EGR passage 60 in the exhaust passage 40 increases, and the differential pressure between the exhaust passage 40 side and the intake passage 30 side of the low pressure EGR valve 62 in the low pressure EGR passage 60 increases. Therefore, the recirculation amount of the exhaust gas through the low pressure EGR passage 60 is adjusted by controlling the opening degree of the low pressure EGR valve 62 and the exhaust shutter valve 48. Note that the exhaust shutter valve 48 is not necessarily required, and may be omitted.

  As shown in FIG. 2, the engine speed sensor 9, the air flow sensor 32, the intake air temperature sensor 33, the accelerator opening sensor 71 for detecting the accelerator opening, and the cooling water temperature (cooling water temperature) of the engine 1 are detected. A sensor value signal such as the cooling water temperature sensor 72 (cooling water temperature detecting means) is input to the control unit 100 that controls the engine 1. The control unit 100 receives a signal relating to information on the current shift range of the automatic transmission from the transmission control device 75 that controls the automatic transmission of the vehicle. Thus, the transmission control device 75 constitutes a shift range detecting means for detecting the shift range of the transmission of the vehicle on which the engine 1 is mounted.

  In the present embodiment, when the engine 1 is idling, the transmission control device 75 is in the traveling range (D range, R range, etc.) and the brake pedal is depressed. Neutral control is performed to reduce the drive transmission force of the transmission so that the transmission is close to neutral. Thus, the transmission control device 75 constitutes drive transmission force reducing means. The neutral control is executed by sliding a clutch in the engaged state in the transmission (a clutch in a fully engaged state when neutral control is not executed). As a result, the creep force is reduced, and the vehicle occupant can maintain the vehicle stop state by simply depressing the brake pedal lightly.

  The transmission control device 75 outputs a neutral control execution signal to the control unit 100 when executing the neutral control, and the neutral control execution signal is also input to the control unit 100.

  The control unit 100 is a controller based on a well-known microcomputer, and includes a central processing unit (CPU) that executes a program, a memory that is configured by, for example, a RAM or ROM, and stores a program and data, and an electrical signal An input / output (I / O) bus.

  Based on the input signal, the control unit 100 determines that the VVL 16, the injector 17, the VGT throttle valve 21, the intake shutter valve 37, the exhaust shutter valve 48, the cooler side EGR valve 54, the cooler bypass side EGR valve 55, and the low pressure EGR valve. 62 is controlled.

  The control unit 100 uses a low pressure EGR target recirculation amount that is a target value of the exhaust gas recirculation amount through the low pressure EGR passage 60 and a target value of the exhaust gas recirculation amount through the high pressure EGR passage 50 according to the operating state of the engine 1. A certain high pressure EGR target reflux amount is determined. In the present embodiment, the control unit 100 is based on signals from the engine speed sensor 9 and the accelerator opening sensor 71, that is, based on the engine speed Ne and the engine load PE, according to the map shown in FIG. The low pressure EGR target reflux amount and the high pressure EGR target reflux amount are determined.

The “LP” region, which is a high load or high rotation region in the map, is a region where exhaust gas recirculation is performed only by the low pressure EGR passage 60. In the map, in the “LP” region, the low pressure EGR target recirculation amount corresponding to the engine speed Ne and the engine load PE is preset, and the high pressure EGR target recirculation amount is preset to 0. As a result, the cooler side EGR valve 54 and the cooler bypass side EGR valve 55 are fully closed. This is because all the exhaust gas is guided to the turbine 20b of the exhaust turbocharger 20 and supercharged in a high load region where torque is required.
The pressure ratio of the compressor 20a of the exhaust turbo supercharger 20 is high, the differential pressure between the exhaust passage 40 side and the intake passage 30 side of the cooler side EGR valve 54 in the cooler side passage 51, and the cooler bypass side passage 52. This is because the exhaust gas recirculation through the high pressure EGR passage 50 can hardly be performed because the differential pressure between the exhaust passage 40 side and the intake passage 30 side of the cooler bypass side EGR valve 55 is small.

  The “cooler side HP + LP” region, which is a medium load or medium rotation region of the map, is a region where exhaust gas recirculation through the cooler side passage 51 of the high pressure EGR passage 50 and exhaust gas recirculation through the low pressure EGR passage 60 is performed. Thus, the exhaust gas is not recirculated through the cooler bypass side passage 52 (the cooler bypass side EGR valve 55 is fully closed). In the map, a low pressure EGR target return amount and a high pressure EGR target return amount corresponding to the engine speed Ne and the engine load PE are set in advance in the “cooler side HP + LP” region.

  In the “cooler bypass side HP + LP” region, which is a low load or low rotation region of the map, exhaust gas recirculation through the cooler bypass side passage 52 of the high pressure EGR passage 50 and exhaust gas recirculation through the low pressure EGR passage 60 are performed. The exhaust gas is not recirculated through the cooler side passage 51 (the cooler side EGR valve 54 is fully closed). In the map, a low pressure EGR target recirculation amount and a high pressure EGR target recirculation amount corresponding to the engine speed Ne and the engine load PE are set in advance in the “cooler bypass side HP + LP” region.

  The control unit 100 is configured such that the low-pressure EGR valve 62, the exhaust shutter valve 48, the cooler-side EGR valve 54, and the cooler-bypass-side EGR valve 55 are opened by the recirculation amount of exhaust gas through the low-pressure EGR passage 60 and the high-pressure EGR passage 50. Control is performed so that the low pressure EGR target recirculation amount and the high pressure EGR target recirculation amount preset in the map are obtained. Thus, the control unit 100 constitutes a valve control device.

  In the present embodiment, the map is further provided with an “idle” region that is applied when the engine 1 is idling. In this “idle” region, the shift of the automatic transmission input from the transmission control device 75 is provided. Depending on whether the range is a travel range (D range, R range, etc.) or a non-travel range (P range, N range), separate low pressure EGR target reflux amount and high pressure EGR target reflux amount are preset. Yes.

  That is, when the engine 1 is in idling operation, the control unit 100 detects that the exhaust by the low-pressure EGR passage 60 and the high-pressure EGR passage 50 when the shift range of the automatic transmission is a non-traveling range as compared to when it is a traveling range. The low pressure EGR valve 62 and the exhaust shutter valve 48 and the high pressure EGR valve (cooler side EGR valve 54 and cooler bypass side EGR valve) are set so that the ratio of the exhaust gas recirculation amount through the high pressure EGR passage 50 to the total gas recirculation amount increases. 55) is controlled. In this embodiment, when the engine 1 is idling, the exhaust shutter valve 48 is always set to a constant value.

  In the present embodiment, when the shift range of the automatic transmission is the non-traveling range during the idling operation of the engine 1, the ratio is set to 100%. That is, the low pressure EGR target recirculation amount at this time is set to 0 in advance, and the opening degree of the low pressure EGR valve 62 is set to 0%, and the exhaust gas is recirculated only by the high pressure EGR passage 50 (low pressure EGR passage 60). Do not recirculate exhaust gas).

  Here, the exhaust gas recirculation by the high-pressure EGR passage 50 is basically performed by the cooler bypass side passage 52 (the opening degree of the cooler side EGR valve 54 is reduced to 0%) as in the “cooler bypass side HP + LP” region. However, it is also possible to recirculate the exhaust gas through the high pressure EGR passage 50 by using the cooler side passage 51 together or by itself. However, when the cooling water temperature detected by the cooling water temperature sensor 72 is lower than a preset temperature (for example, 50 ° C. to 60 ° C.) (that is, when it is cold before the completion of warming), the high pressure EGR passage 50 When the exhaust gas is recirculated, the opening degree of the cooler side EGR valve 54 is preferably set to 0%. This is because when the cooling water temperature is lower than the set temperature, condensed water is generated at the location of the high-pressure EGR cooler 53 in the cooler-side passage 51, which is mixed with soot and deposits are generated. In particular, since the exhaust gas flowing through the high pressure EGR passage 50 is before passing through the exhaust purification device 43, it contains a large amount of soot. Therefore, deposits are easily generated, and the deposit causes the cooler side passage 51 to flow. In order to prevent this, the opening degree of the cooler side EGR valve 54 is set to 0%.

  On the other hand, when the shift range of the automatic transmission is the travel range, the ratio is set to exceed 0% and less than 100%, and the exhaust gas is recirculated through the low pressure EGR passage 60 and the high pressure EGR passage 50. The exhaust gas recirculation through the high-pressure EGR passage 50 at this time is also performed by the cooler bypass side passage 52 (the opening degree of the cooler side EGR valve 54 is set to 0%) as in the case where the shift range is the non-traveling range. . As described above, it is preferable to do so particularly when the cooling water temperature is lower than the set temperature.

  The ratio when the shift range is the traveling range is preferably low from the viewpoint of vehicle start response, but is preferably high from the viewpoint of preventing condensed water from accumulating in the intercooler 35. Set in consideration of the viewpoint. However, since the speed change range is a travel range, it is considered that the vehicle occupant is highly willing to travel. Therefore, it is preferable to emphasize the vehicle start response.

  The exhaust gas recirculation control operation by the control unit 100 will be described based on the flowchart of FIG.

  In the first step S1, the accelerator opening degree Acc is determined by the accelerator opening degree sensor 71, the engine speed Ne is determined by the engine speed sensor 9, the shift range of the automatic transmission is cooled by the transmission control device 75, and the cooling water temperature sensor 72 is cooled. Read each water temperature Tw.

  In the next step S2, whether or not the operating state of the engine 1 is in the “idle” region is determined according to the map shown in FIG. 3 from the engine speed Ne and the accelerator opening Acc (corresponding to the engine load PE). When the determination at step S2 is YES, the process proceeds to step S3. When the determination at step S2 is NO, the process proceeds to step S6.

  In step S3, it is determined whether or not the shift range of the automatic transmission is a non-traveling range. When the determination in step S3 is YES, the process proceeds to step S4, and the low pressure EGR valve 62, the exhaust shutter valve 48, the cooler side EGR valve 54, and the cooler bypass side are provided so as to recirculate the exhaust gas only through the high pressure EGR passage 50. The opening degree of the EGR valve 55 is controlled, and then the process returns.

  On the other hand, when the determination in step S3 is NO, the process proceeds to step S5, and the low-pressure EGR valve 62, the exhaust shutter valve 48, the cooler-side EGR valve are used to recirculate the exhaust gas through the low pressure EGR passage 60 and the high pressure EGR passage 50. 54 and the opening degree of the cooler bypass EGR valve 55 are controlled, and then the process returns.

  In step S6 that proceeds when the determination in step S2 is NO, the opening degree of the low pressure EGR valve 62, the exhaust shutter valve 48, the cooler side EGR valve 54, and the cooler bypass side EGR valve 55 is controlled according to the map. Return later.

  Therefore, in the exhaust gas recirculation control, when the shift range of the automatic transmission is the non-traveling range during the idle operation of the engine 1, the exhaust gas recirculation is performed only by the high pressure EGR passage 50. Condensed water can be prevented from accumulating. Even if the exhaust gas is not recirculated through the low-pressure EGR passage 60 as described above, when the shift range of the transmission is the non-traveling range, the vehicle driver's willingness to travel is low, and the problem of the start response of the vehicle is Does not occur. On the other hand, when the shift range of the automatic transmission is the travel range, exhaust gas recirculation is performed through the low pressure EGR passage and the high pressure EGR passage, so that the start response of the vehicle can be improved. In this way, even when the exhaust gas is recirculated through the low pressure EGR passage 60 when the shift range is the traveling range, the possibility that the vehicle will start in a short time is high, so that condensed water does not easily accumulate in the intercooler 35. When the vehicle starts, the condensed water accumulated in the intercooler 35 is sucked into the engine.

  FIG. 5 is a flowchart showing another exhaust gas recirculation control operation by the control unit. In this exhaust gas recirculation control, even if the shift range of the automatic transmission is the travel range, exhaust gas recirculation may be performed only by the high-pressure EGR passage 50 as in the non-travel range.

  That is, in the first step S21, the accelerator opening degree Acc is determined by the accelerator opening degree sensor 71, the engine speed Ne is determined by the engine speed sensor 9, the shift range of the automatic transmission is determined by the transmission control device 75, and the cooling water temperature sensor 72 is selected. The cooling water temperature Tw is read, and the intake air temperature Ta is read from the intake air temperature sensor 33. When the transmission control device 75 outputs a neutral control execution signal, the neutral control execution signal is input.

  In the next step S22, it is determined from the engine speed Ne and the accelerator opening Acc (corresponding to the engine load PE) whether or not the operating state of the engine 1 is in the “idle” region according to the map shown in FIG. When the determination at step S22 is YES, the process proceeds to step S23. When the determination at step S22 is NO, the process proceeds to step S31.

  In step S23, it is determined whether or not the shift range of the automatic transmission is a non-traveling range. When the determination in step S23 is YES, the process proceeds to step S24, and the low pressure EGR valve 62, the exhaust shutter valve 48, the cooler side EGR valve 54, and the cooler bypass side are provided so as to recirculate the exhaust gas only by the high pressure EGR passage 50. The opening degree of the EGR valve 55 is controlled, and in the next step S25, the timer T is reset, and then the process returns. The timer T counts the time during which the state of the travel range continues when the shift range of the automatic transmission is the travel range.

  On the other hand, when the determination in step S23 is NO, the process proceeds to step S26, in which it is determined whether or not the intake air temperature Ta is lower than a predetermined temperature Ta0. When the determination in step S26 is YES, the process proceeds to step S24. When the determination in step S26 is NO, the process proceeds to step S27, and whether or not the transmission control device 75 is executing neutral control. Determine.

  When the determination in step S27 is YES, the process proceeds to step S24. On the other hand, when the determination in step S27 is NO, the process proceeds to step S28, and the timer T that is started in step S30 described later is equal to or greater than the predetermined time T0. It is determined whether or not there is.

  When the determination in step S28 is YES, the process proceeds to step S24. On the other hand, when the determination in step S28 is NO, the process proceeds to step S29, and the exhaust gas is recirculated through the low pressure EGR passage 60 and the high pressure EGR passage 50. Therefore, the opening degree of the low pressure EGR valve 62, the exhaust shutter valve 48, the cooler side EGR valve 54 and the cooler bypass side EGR valve 55 is controlled, and the timer T is started in the next step S30, and then the process returns.

  In step S31 that proceeds when the determination in step S22 is NO, the opening degree of the low pressure EGR valve 62, the exhaust shutter valve 48, the cooler side EGR valve 54, and the cooler bypass side EGR valve 55 is controlled according to the map. Return later.

  With the exhaust gas recirculation control, even if the shift range of the automatic transmission is the travel range, when the intake air temperature Ta by the intake air temperature sensor 33 is lower than the predetermined temperature Ta0, the transmission control device 75 is executing neutral control. In some cases, or when the state of the travel range continues for a predetermined time T0 or more, the ratio is set to the same ratio (100% in the control) as in the non-travel range.

  That is, when the intake air temperature Ta is lower than a predetermined temperature Ta0 (for example, 0 ° C. to 5 ° C.), the condensed water easily accumulates in the intercooler 35 and the condensed water easily freezes, but the exhaust gas by the low-pressure EGR passage 60 By not performing the reflux, it is possible to reliably prevent the condensed water from accumulating in the intercooler 35 and freezing.

  Further, when the transmission control device 75 is executing the neutral control, the brake pedal is depressed, so it is considered that the vehicle driver's driving intention is low. Therefore, at this time, by setting the ratio to the same high ratio as in the non-traveling range (100% in the control above), it is possible to prevent the condensed water from accumulating in the intercooler 35 as much as possible.

  Further, when the state where the automatic transmission is in the travel range continues for a predetermined time T0 or more, there is a high possibility that a large amount of condensed water will accumulate in the intercooler 35. At this time, the above ratio is set to the non-travel range. By setting the ratio to the same high rate as in the above case (100% in the above control), it is possible to prevent a large amount of condensed water from accumulating in the intercooler 35.

  The present invention is not limited to the embodiment described above, and can be substituted without departing from the spirit of the claims.

  For example, in the above embodiment, when the shift range of the automatic transmission is the non-traveling range, the exhaust gas is recirculated only by the high pressure EGR passage 50, but the exhaust by the low pressure EGR passage 60 and the high pressure EGR passage 50 is performed. Gas recirculation may be performed. In this case, the ratio when the vehicle is in the non-traveling range may be less than 100% and higher than the ratio when the vehicle is in the traveling range. In this case, even if the shift range of the automatic transmission is the travel range, when the intake air temperature Ta is lower than the predetermined temperature Ta0, the transmission control device 75 is executing neutral control, or When the state of the travel range continues for a predetermined time T0 or more, the ratio may be set to the same ratio as that of the non-travel range. However, when the intake air temperature Ta is lower than the predetermined temperature Ta0, it is better to set the opening of the low pressure EGR valve 62 to 0% regardless of the shift range.

  Moreover, in the said embodiment, although the engine 1 is provided with only one exhaust turbo supercharger 20, two or more exhaust turbo superchargers may be provided. In this case, the low-pressure EGR passage 60 connects the downstream portion of the turbine located on the most downstream side in the exhaust passage 40 and the upstream portion of the compressor located on the most upstream side in the intake passage 30. . Further, the high-pressure EGR passage 50 includes a portion on the upstream side of the turbine located on the most upstream side in the exhaust passage 40 and a downstream side of the intercooler 35 located on the further downstream side of the compressor located on the most downstream side in the intake passage 30. Will be connected.

  The above-described embodiments are merely examples, and the scope of the present invention should not be interpreted in a limited manner. The scope of the present invention is defined by the scope of the claims, and all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  The present invention includes an exhaust turbocharger having a turbine disposed in an exhaust passage of an engine and a compressor disposed in an intake passage, and an intercooler disposed in the intake passage on the downstream side of the compressor. A low-pressure EGR passage connecting the exhaust passage downstream of the turbine and the intake passage upstream of the compressor, and a low-pressure EGR disposed in the low-pressure EGR passage and changing a cross-sectional area of the low-pressure EGR passage. A high-pressure EGR passage connecting the valve, the exhaust passage upstream of the turbine and the intake passage downstream of the intercooler, and the high-pressure EGR passage, and changing the cross-sectional area of the high-pressure EGR passage Engine exhaust gas, comprising: a high-pressure EGR valve that controls, and a valve control device that controls an opening degree of the low-pressure EGR valve and the high-pressure EGR valve Useful to scan recirculation control system.

1 Engine 20 Exhaust Turbocharger 20a Compressor 20b Turbine 30 Intake Passage 33 Intake Air Temperature Sensor (Intake Air Temperature Detection Means)
40 Exhaust passage 48 Exhaust shutter valve 50 High pressure EGR passage 51 Cooler side passage 52 Cooler bypass side passage 53 High pressure EGR cooler 54 Cooler side EGR valve (high pressure EGR valve)
55 Cooler bypass EGR valve (high pressure EGR valve)
60 Low pressure EGR passage 62 Low pressure EGR valve 72 Cooling water temperature sensor (cooling water temperature detecting means)
75 Shift control device (shift range detection means) (drive transmission force reduction means)
100 Control unit (valve control device)

Claims (5)

An exhaust turbocharger having a turbine disposed in the exhaust passage of the engine and a compressor disposed in the intake passage; an intercooler disposed in the intake passage downstream of the compressor; A low pressure EGR passage connecting the exhaust passage on the downstream side and the intake passage upstream of the compressor, a low pressure EGR valve disposed in the low pressure EGR passage and changing a cross-sectional area of the low pressure EGR passage, A high pressure EGR passage that connects the exhaust passage upstream of the turbine and the intake passage downstream of the intercooler, and a high pressure EGR valve that is disposed in the high pressure EGR passage and changes a cross-sectional area of the high pressure EGR passage And a low-pressure EGR valve and a valve control device for controlling the opening degree of the high-pressure EGR valve. An apparatus,
A shift range detecting means for detecting a shift range of a transmission of a vehicle on which the engine is mounted;
In the idle control of the engine, the valve control device is configured such that when the shift range detected by the shift range detecting means is a non-traveling range, the low-pressure EGR passage and the high-pressure EGR are compared to when the shifting range is a traveling range. The opening degree of the low pressure EGR valve and the high pressure EGR valve is controlled so that the ratio of the recirculation amount of the exhaust gas through the high pressure EGR passage to the total recirculation amount of the engine exhaust gas through the passage increases. An exhaust gas recirculation control device for an engine characterized by comprising: The exhaust gas recirculation control apparatus for an engine according to claim 1,
An intake air temperature detecting means for detecting the temperature of the intake air taken into the intake passage;
In the idling operation of the engine, when the temperature of the intake air detected by the intake air temperature detection unit is lower than a predetermined temperature, the valve control device is independent of the shift range detected by the shift range detection unit. An exhaust gas recirculation control apparatus for an engine, characterized in that the opening degree of the low pressure EGR valve is set to 0%. The exhaust gas recirculation control device for an engine according to claim 1 or 2,
The high-pressure EGR passage has a cooler-side passage in which a high-pressure EGR cooler for cooling exhaust gas passing through the interior is disposed, and a cooler bypass-side passage that bypasses the high-pressure EGR cooler,
The high-pressure EGR valve includes a cooler-side EGR valve disposed in the cooler-side passage and changing a cross-sectional area of the cooler-side passage, and a disconnection of the cooler bypass-side passage disposed in the cooler bypass-side passage. Consists of a cooler bypass side EGR valve that changes the area,
A cooling water temperature detecting means for detecting the temperature of the cooling water of the engine;
When the temperature of the cooling water detected by the cooling water temperature detecting means is lower than a preset temperature during the idling operation of the engine, the valve control device controls the exhaust gas by the high pressure EGR passage. An exhaust gas recirculation control device for an engine, wherein when performing recirculation, the opening degree of the cooler side EGR valve is set to 0%. The exhaust gas recirculation control device for an engine according to any one of claims 1 to 3,
In the idling operation of the engine, the valve control device is configured such that, even if the shift range detected by the shift range detecting means is a travel range, the travel range is continued for a predetermined time or longer. An exhaust gas recirculation control device for an engine, characterized in that the openings of the low pressure EGR valve and the high pressure EGR valve are controlled so that the ratio is the same as that in the non-traveling range. . In the exhaust gas recirculation control device for an engine according to any one of claims 1 to 4,
When the engine is in idle operation, the transmission further includes drive transmission force reducing means for reducing the transmission transmission force of the transmission when the transmission shift range is the travel range and the brake pedal is depressed.
In the idling operation of the engine, the valve control device is configured such that, even if the shift range detected by the shift range detection unit is a travel range, the drive transmission force is reduced by the drive transmission force reduction unit. The exhaust gas recirculation of the engine is configured to control the opening degree of the low pressure EGR valve and the high pressure EGR valve so that the ratio is the same as that in the non-traveling range. Control device.

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